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BARIUM PEROXIDE

53

with hydrogen sulphide, should not give a brown (iron, copper, lead] or
white turbidity (zinc}.

5. Determination of the Antimony.0-5 gram is dissolved in 50 c.c.
of water and 10% sodium bicarbonate solution added to give an alkaline
reaction; should a little precipitate form, it is removed by addition of a
little Rochelle salt dissolved in water. Starch paste is added and the
liquid titrated with N/io-iodine until a blue colour, persisting for a short
time, is obtained, i c.c. N/io-iodine = 0-00721 gram Sb203 = 0-00601
gram Sb.

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* *

Chemically pure tartar emetic contains 43-4% Sb2O3, and the commercial
products usually contain 42-43 %. For use in dyeing it should be free especially
from iron, whilst for medicinal purposes it should contain none of the above
impurities and should hence answer all the tests 1-4.

As substitutes for tartar emetic in dyeing, various other antimony com-
pounds are used, such as double oxalates and fluovides of antimony and potassium
or sodium and ammonium, or lactates of antimony and sodium or calcium (anti-
monin}. In these products the antimony is determined as in 5 (above), and
the test for iron made.

BARIUM   CHLORIDE

Bad 2 + 2H20 = 244-29

Colourless crystals, soluble in water, insoluble in cone, hydrochloric
acid. The commercial salt for technical uses may be yellowish or greyish
and in fine powder (flour).

It may contain, as impurities, iron, calcium chloride (hygroscopic)
and potassium chloride (sometimes large quantities). In general, the
following tests are sufficient :

1.  Solubility, Heavy Metals.i gram, dissolved in 10 c.c. of water,
should give a clear, neutral solution which, when acidified with hydrochloric
acid, is not altered by potassium ferrocyanide (iron) or hydrogen sulphide,
even after being made alkaline with ammonia (other metals}.

2.  Lime and Alkalies.5 grams, dissolved in 50 c.c. of water, are
precipitated in the hot by dilute sulphuric acid and filtered :  the filtrate
should not be rendered turbid by alcohol and, when evaporated to dryness
and ignited, it should leave no appreciable residue.

BARIUM   PEROXIDE

Ba02 = 169-37 (169)

White or greyish powder, insoluble in water ; with dilute sulphuric acid
it gives hydrogen peroxide.

Its value depends essentially on the proportion of Ba02, which is deter-
mined in the following way : 0-2-0-3 gram is introduced, gradually and
with shaking, into 300 c.c. of 10% sulphuric acid, the hydrogen peroxide
thus formed being titrated with N/5-permanganate solution ; i c.c. N/5-
permanganate  0-0169 gram Ba02.

Commercial barium peroxide usually contains 80-85% % BaO2, the remainder
being barium oxide and a few other impurities ; some of the better grades con-
tain, however, 90-91% BaO2. saturated